Paolo Di Canio has painted a remarkable picture of wide-ranging indiscipline in his Sunderland squad, claiming that the levels of "arrogance" and "ignorance" are worse than those he encountered at Swindon Town, his previous club, and making it plain he wants to see sweeping changes in personnel over the summer.

The manager opened up as he explained the reasons for the omission of Phil Bardsley from the squad that travelled to London for Sunday's 1-0 defeat against Tottenham Hotspur. Di Canio had been incandescent when he saw a photograph of the defender lying on a casino floor and covered in £50 notes.

Bardsley and some of his team-mates had gone out to watch Arsenal's televised victory over Wigan Athletic on Tuesday night – the result that secured Sunderland's Premier League survival – and he went on to the casino with one of them, Matt Kilgallon.

Di Canio said that the photograph of Bardsley, which was posted on a website, had disgusted him, but it quickly became apparent that the indiscretion was not the only thing that had bothered him since he took over from Martin O'Neill at the end of March.

Phil Bardsley was omitted from the squad that travelled to the Tottenham game after Paolo Di Canio saw a photograph of the defender lying on a casino floor and covered in £50 notes. Photograph: Clive Brunskill/Getty Images

Di Canio fined seven of his squad last week alone for various breaches of the code of conduct that he has introduced and he spoke with scarcely concealed contempt at the attitude of certain players, dwelling upon what he sees as their flippant disregard for the basic rules of the profession.

"At the beginning, I thought it was difficult," Di Canio said. "Week by week … daily … I discover that we have more problems than I expected. That's why I said to everybody we made a miracle [to avoid relegation] because what we discovered this week is only one aspect of the problems we've got. It doesn't mean that everybody goes out every night and has a drink session. No. I'm talking in general about professionalism.

"This week, there have been seven fined and this morning, once again … a player that I could not involve in the squad for a different reason decided: 'I don't train today.' He said he had food poisoning. He made the diagnosis. Sorry, are you the doctor? The doctor tried to contact him. Three hours, he switched off his telephone. This is the situation at Sunderland."

Bardsley accepted being left out of the squad and denied that he had been drunk. But Di Canio tore into him. "What we saw is something really wrong, it's disgusting me even to see the image for the club," he said. "It's not about going out late with your friend and getting back at two, three o'clock, which is late but you can close one eye. But full of alcohol?

"It takes three or four days [to recover]. I realised in the morning [on Wednesday], before I had seen the picture, that I wouldn't play Phil on Sunday. I told my assistant. Why? I speak to him [Bardsley] and he look in the sky. He can't listen. He's blurry.

"We have a fantastic academy … but if we don't punish this kind of behaviour, how do they grow up? Thinking they can laugh about what they saw on the website picture? Maybe they think it's fantastic; to be like a gangster. But what mentality are we going to deliver?"

Di Canio spoke with rising levels of anger about the fines that he had handed out last week. One, he said, was to an injured player who left the club at lunchtime and switched off his phone. He also mentioned an incident after the 6-1 defeat at Aston Villa on 29 April when a few players ambled in 20 minutes late for a 4pm meeting the following day.

"When I gave the fine the day after [to the injured player], he was surprised," Di Canio said. "Before, it was normal. To leave and switch off the phone, and the day after everybody forgot because it was more convenient. They don't have friction with the player. I don't care about having an argument with my players.

"This is the behaviour in the Premier League, at a club that every year spent millions and millions. It's not acceptable. I thought that at Swindon … arrogant, ignorant footballers … I have to tell you, unfortunately, I found a worse environment in terms of discipline at this club. This is what I found so we have to change completely."

Di Canio was asked whether he would be prepared to keep the indisciplined players. He said he was not. "We need to bring in six or seven players," he added, "… who know how to behave and have a professional ethic. Otherwise, for me, it's difficult. The owner knows many things. He told me: 'We are going to change many things. Relax.' So it sounds that he supports me completely. We will see in the future."